The proposed study will determine the effects selected environmental contaminants have on the immune response of mice to a growing tumor and the effects of contaminant-induced immune alteration on the incidence and growth rate of tumors in intoxicated animals. Several parameters of immunity will be assessed at various times after tumor inoculation. Assays will include lymphocyte-mediated cytotoxicity, serum blocking activity, lymphokine production, and lymphocyte blastogenesis. In addition, contaminant-exposed animals will be monitored for changes in in vivo tumor growth rate parameters (regression, progression, metastases formation). Contaminants (lead, cadmium, arsenic, PCBs) will be administered in the drinking water or in food for 15 weeks prior to tumor inoculation and immune testing. Subclinical doses of the contaminants will be includes. Two tumor systems, the B16 melanoma and MSV-induced sarcoma, will be utilized to compare the differences in immune function between a progressive and a regressive tumor in the presence of environmental contaminants.